There is a need for improved measurement of cryogenic flows of varying fluids, temperatures, flow rates, and pipe diameters in a noninvasive manner. Specifically, instrumentation that may used in rocket engine test areas is needed. Commercially available flowmeters lack low temperature capabilities. Ultrasonic instrumentation is a potential alternative for traditional cryogenic flow measurement because of its noninvasive nature. Optimization of positioning ultrasonic transducers would greatly increase the versatility of cryogenics instrumentation.
An acoustical or ultrasonic wave is subject to the mediums it must traverse. Interfaces between dissimilar materials within the ultrasonic signal path of flow instrumentation cause an ultrasonic wave to be subjected to attenuation, reflection, and refraction. The consequences of these effects may be minimized through improved design and development of ultrasonic instrumentation. Within an ultrasonic flow measurement tool there are many interfaces that the ultrasonic wave must traverse. In practice, the connection of ultrasonic transducers to the exterior of pipe typically complicates the interface issue and results in appreciable setup and calibration time.
Initially, fundamental research included the transit methods of measurement for industrial applications. Early research revealed the underlying equations used to calculate transit times in isotropic materials in different modes of propagation. However, as the technology matured, later work expanded to new industrial applications and improved ultrasonic instrumentation. Unfortunately, later work publications did not provide details because of competitive pressures.
Ultrasonic flow measurement technology monitors a generated signal between a transmitter and a receiver to determine the location of the signal within an object, such as a pipe. Conventional ultrasonic technology uses software to calculate the predicted location of a signal received from an ultrasonic transmitter. The calculations involve variables that may be mere estimates and excludes some variables that may be considered negligible.
Most modern ultrasonic flow instrumentation requires calculated transducer positioning and manual setup. The signal path of the instrumentation is altered by pipe and fluid properties including impedance, reflection, refraction, diffraction and scattering, absorption, and multiple boundary interfaces. Only by identifying the location of the optimum waveform can the combination effects of all these variables be accurately determined.
The current methods for predicting signal location may not be acceptable in applications requiring a more exact determination of flow. Thus, a system for measuring a received signal directly, after all effects of system variables have had influence on the signal, and automatically determining the optimal position for the receiving transducer is needed.
The aerospace testing industry would benefit from an improvement in ultrasonic flow instrumentation. The industry requires instrumentation with low temperature capabilities that can measure cryogenic flows in a noninvasive manner in field applications with varying fluids, temperatures, flow rates, and pipe diameters. An ultrasonic system that automatically determines the optimal receiving transducer position while accounting for the various system effects is desirable. Developing ultrasonic instrumentation in combination with computational fluid dynamics software is also desirable.